Traditionally, there was no uppercase and lowercase. These were actually just stylistic variations of the same letters. First, there were majuscules (uppercase only), then came minuscules (lower case). Following another trend of highlighting certain letters, e.g., the first in a sentence, for example in red ink, eventually majuscules were used for this purpose. Thus, uppercase and lowercase.
Edit: "u" was another stylistic variation of "v" in minuscule alphabets. So the use of both of them side by side is rather an anachronism as it combines forms of two separate eras.
Edit: Regarding the long form of "s", this is also an important part of the ligature "ß". There's still an ongoing discussion, whether it is for "ſs" (ss) or "ſʒ" (sz), and, if "ß" should be split into "SS" or "SZ" in German uppercase writing. (While entity escaping suggests "szlig", some sources and old typographic forms indicate that it may have been "ſs" originally.)
And the reason that they are named "uppercase" and "lowercase" is that in the early days of movable type, the majuscule letters were stored in a case above the miniscule letters.
Furthermore, Roman and Italic are two entirely different styles of characters. For highlighting purposes, printers started using Italic within Roman text, and eventually pairs of Roman and Italic fonts became identified with each other, so that now typefaces generally include both of them.
It may also be interesting that these styles of writing characters originally went with different styles of filling a page. Around the first millennium horror vacui reigned the scriptoria and scribes tended to fill the whole of the page with as least of white space as possible. If there was space left at the end of a line or page, the last words were repeated, often framed by "va (...) cat". This style coincided with broken letter styles favoring the similarities in the various character forms.
(We may observe that the upcoming use of white space in writing in order to structure text roughly coincides with the introduction of zero into the number system. We may also observe that the use of zero was already implied by the Roman abacus, but didn't propagate to writing numbers. This may be seen in the context of Roman writing dismissing interpunctuations originally imported from the Greek and eventually also dismissing spaces between words, as it was considered important for a reader to immerse in the text in order to reveal its meaning. This approach to writing and reading may also shed some light on the horror vacui that may be observed in medieval writing. For an opposite approach we may consider the Summa Theologiae, breaking down the text in structure and form so it provides a quick and easy orientation for where in the text we currently are. This approach brings also some new characters, like "¶" to mark the beginning of a paragraph. – Historically, there's been an ongoing discussion whether to favor legibility or rather illegibility in writing and letter forms, which is linked to the question, whether a text should reveal its meaning quickly, or rather resist a cursory reading.)
All of that is correct, but I was thinking more of the Shakespearean era after the modern use of uppercase/lowercase arose but before V and U split into different letters. So back then you had, for example, "love" written as loue.
Edit: "u" was another stylistic variation of "v" in minuscule alphabets. So the use of both of them side by side is rather an anachronism as it combines forms of two separate eras.
Edit: Regarding the long form of "s", this is also an important part of the ligature "ß". There's still an ongoing discussion, whether it is for "ſs" (ss) or "ſʒ" (sz), and, if "ß" should be split into "SS" or "SZ" in German uppercase writing. (While entity escaping suggests "szlig", some sources and old typographic forms indicate that it may have been "ſs" originally.)